In Vitro Evaluation of Antibodies

As we know, a complete monoclonal antibody includes an antigen-binding fragment (Fab) and a fragment crystallizable region (Fc). The Fab can bind to a tumor-associated antigen, while the Fc plays an important role in metabolic pathways, as well as in IgG cellular functions.

The molecular sequence and subtype of antibodies will affect the effector functions. Such effector functions include the antibody dependent cellular cytotoxicity (ADCC) triggered by Fc binding to the FcγRIII receptor (CD16A) of NK. The Fc can also bind with serum complement molecules (C1q) to form a membrane attack complex (MAC) that triggers complement-dependent cytotoxicity (CDC). When the Fc binds with macrophage receptors—namely FcγRIII (CD16A), FcγRII (CD32A) and FcγRI (CD64)—the antibody-dependent cellular phagocytosis (ADCP) is triggered.

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FAQ

Why are Bispecific Antibodies Better?

The effectiveness of double-target bispecific antibody or single-target double-epitope bispecific antibody may be superior to the combination of two single-target monoclonal antibodies.
A dual-target antibody-drug molecule may have fewer side effects than a single-target antibody-drug.
A dual-target antibody-drug molecule may solve the mechanism of action that combination drugs cannot solve.
Killing tumors induced by mediated immune cells; Blocking dual target signal, playing unique or repetitive functions, preventing effectively drug resistance; It has more substantial specificity, targets and reduces off-target toxicity. Reducing effectively the cost of treatment.
What are Bispecific Antibodies

Bispecific antibodies (BsAB), also known as bifunctional antibodies, can simultaneously recognize and bind two different antigens and epitopes and block two different signaling pathways to exert their effects.
How to Generate Bispecific Antibody?

The preparation of bispecific antibodies mainly includes the two-hybrid tumor cell method, chemical coupling, recombinant gene preparation, and other methods.
Recombinant DNA technology is currently the most used technology for the preparation of BsAb. .
Types of Bispecific Antibodies

With the development of technology and platform, bispecific antibody-hydrolyzed forms have been developed into more than 100 molecular forms. The whole can be divided into:
• Symmetric formats:
Symmetric bispecific antibodies retain the Fc region and are more similar to natural antibodies but differ in size and structure. These differences may negatively affect the beneficial properties associated with natural antibodies, such as stability and solubility, which may compromise the stability of these bispecific antibodies' physicochemical and/or pharmacokinetic properties.
• Asymmetric formats:
In this category, most forms used for this antibody generation attempt to preserve the native structure of natural antibodies as much as possible to maintain the associated functional characteristics and good quality attributes so that most of the asymmetric formats of bispecific antibodies are very similar to the natural antibody. They are considered to have the lowest immunogenicity potential.
• Fragment formats:
Fragment-based bispecific antibodies combine multiple antibody fragments in a single molecule, without Fc region (crystallized fragment, as opposed to antigen-bound fragment Fab), and avoid chain-related problems. The advantages are high yield and low cost; the disadvantages are relatively short half-life.
In addition, fragment-based bispecific antibodies may have stability and polymerization problems.

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